Class 9
Chapter 5 Class 9 - The Fundamental Unit of Life

How do substances like CO 2 and water move in and out of the cell? Discuss.



Cells have a semi-permeable membrane (cell membrane) as the outer covering. 

  • Substances inside the cell and those in the surroundings can move from areas of high concentration to areas of low concentration .

CO 2 as well as water follow this principle.

  • If an animal or plant cell is put in water, water will move across the walls of the cell. 
  • If the water content is higher outside the cell than inside it , water will move into the cell, thus causing it to swell up.
  • If the water content is higher inside the cell than outside it , water will move from the cell into the surrounding, thus causing it to shrivel up.
  • Similarly, CO 2 can also move in and ou t of a cell.
  • The process by which it happens is called diffusion .
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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo